Method of displaying labels on maps of wireless communications devices using pre-rendered characters

Abstract

Labels can be rendered on a map displayed on a wireless communications device by using pre-rendered characters. The pre-rendered characters can be pre-rotated to one of a number of angular orientations and stored as a variable transparency bitmap for rapid overlaying on the map. The bitmap can include an array or grid of characters wherein each row has a unique orientation, for example, ranging from zero to ninety degrees. Rotations of 90 to 360 degrees can then be achieved by reflecting the characters about vertical or horizontal axes. Overlaying pre-rotated characters is more computationally efficient than computing rotations for each character when rendering the label.

The invention claimed is: 
     
       1. A method of rendering a label on a map displayed on a wireless communications device, the method comprising:
 obtaining label data for rendering the label on the map by downloading the label data to the wireless communications device over a wireless link; 
 determining an appropriate orientation on the map for each character of the label; 
 determining color attributes of a label position for the label on the map; 
 selecting a variable transparency bitmap comprising a set of pre-rotated characters that correspond to the orientation and further having a background color corresponding to the color attributes of the label position, wherein the background color of the variable transparency bitmap is adjusted to concord with the color attributes of the label position; and 
 rendering each character at the appropriate orientation on the map displayed on the wireless communications device by overlaying pre-rendered characters on the map from the variable transparency bitmap with the background color corresponding to the color attributes of the label position. 
 
     
     
       2. The method as claimed in  claim 1  wherein the step of rendering the characters comprises overlaying onto the map pre-rotated characters from the variable transparency bitmap wherein pixels along edges of the pre-rotated characters are semi-transparent and anti-aliased. 
     
     
       3. The non-transitory computer-readable medium comprising code which when loaded into memory and executed on a processor of a wireless communications device performs the steps of  claim 2 . 
     
     
       4. The method as claimed in  claim 1  wherein the pre-rendered characters comprise a plurality of sets of pre-rotated punctuation symbols, numbers, uppercase letters and lowercase letters, wherein each of the plurality of sets of pre-rotated characters has a unique angular orientation. 
     
     
       5. The non-transitory computer-readable medium comprising code which when loaded into memory and executed on a processor of a wireless communications device performs the steps of  claim 4 . 
     
     
       6. The method as claimed in  claim 1  wherein the pre-rendered characters comprise a plurality of sets of pre-rotated punctuation symbols, numbers, uppercase letters and lowercase letters that are pre-rotated at discrete angular intervals of 10 degrees, ranging between 0 degrees and 90 degrees, whereby character orientations corresponding to rotations of 90 to 360 degrees can be achieved by reflecting the pre-rotated characters about vertical or horizontal axes. 
     
     
       7. The non-transitory computer-readable medium comprising code which when loaded into memory and executed on a processor of a wireless communications device performs the steps of  claim 6 . 
     
     
       8. The method as claimed in  claim 1  further comprising steps of:
 determining whether any of the characters of the label require special text effects; and 
 overlaying pre-rendered characters having text effects on the map. 
 
     
     
       9. The non-transitory computer-readable medium comprising code which when loaded into memory and executed on a processor of a wireless communications device performs the steps of  claim 8 . 
     
     
       10. The method as claimed in  claim 1  wherein the step of rendering the label comprises a step of overlaying onto the map one or more pre-rotated characters from the bitmap structured as an array wherein each row contains a set of pre-rotated characters having a common orientation. 
     
     
       11. The non-transitory computer-readable medium comprising code which when loaded into memory and executed on a processor of a wireless communications device performs the steps of  claim 10 . 
     
     
       12. The method as claimed in  claim 10  wherein the array comprises ten rows of pre-rotated characters, each having a different orientation, thus providing pre-rotated characters for every 10-degree interval ranging from a first row having zero rotation to a tenth row having a 90-degree rotation. 
     
     
       13. The non-transitory computer-readable medium comprising code which when loaded into memory and executed on a processor of a wireless communications device performs the steps of  claim 12 . 
     
     
       14. The method as claimed in  claim 12  wherein the step of rendering the label comprises a step of reflecting each pre-rotated character about vertical or horizontal axes to obtain desired character rotations of 90 to 360 degrees. 
     
     
       15. The non-transitory computer-readable medium comprising code which when loaded into memory and executed on a processor of a wireless communications device performs the steps of  claim 14 . 
     
     
       16. A non-transitory computer-readable medium comprising code which when loaded into memory and executed on a processor of a wireless communications device performs the steps of  claim 1 . 
     
     
       17. A wireless communications device for displaying a map on the wireless communications device, the wireless communications device comprising:
 an input device for enabling the device to download map data to the wireless communications device over a wireless link, the map data including label data, for rendering the map and at least one label on the map; 
 a memory for storing pre-rendered characters; 
 a processor for determining an appropriate orientation for each character in the label, for determining color attributes of a label position for the label on the map, for selecting a variable transparency bitmap comprising a set of pre-rotated characters that correspond to the orientation and further having a background color corresponding to the color attributes of the label position, wherein the background color of the variable transparency bitmap is adjusted to concord with the color attributes of the label position, and for overlaying the pre-rendered characters on the map from the variable transparency bitmap with the background color that corresponds to the color attributes of the label position; and 
 a display for displaying the pre-rendered characters of the label on the map. 
 
     
     
       18. The wireless communications device as claimed in  claim 17  wherein the pre-rendered characters comprise sets of pre-rotated characters, each set having a unique orientation. 
     
     
       19. The wireless communications device as claimed in  claim 17  wherein pixels along edges of the pre-rotated characters are semi-transparent and anti-aliased. 
     
     
       20. The wireless communications device as claimed in  claim 17  wherein the pre-rendered characters comprise a plurality of sets of pre-rotated punctuation symbols, numbers, uppercase letters and lowercase letters that are pre-rotated at discrete angular intervals of 10 degrees, ranging between 0 degrees and 90 degrees, whereby character orientations corresponding to rotations of 90 to 360 degrees can be achieved by reflecting the pre-rotated characters about vertical or horizontal axes. 
     
     
       21. The wireless communications device as claimed in  claim 17  wherein the bitmap is structured as an array wherein each row contains a set of pre-rotated characters having a common orientation. 
     
     
       22. The wireless communications device as claimed in  claim 21  wherein the array comprises ten rows of pre-rotated characters, each having a different orientation, thus providing pre-rotated characters for every 10-degree interval ranging from a first row having zero rotation to a tenth row having a 90-degree rotation. 
     
     
       23. The wireless communications device as claimed in  claim 17  wherein the pre-rendered characters comprise both pre-rotated characters and characters with special text effects.